Busybodies trolling for information on St. Jerome’s bartender Luc Carl won’t get it from his co-workers. Since Carl’s old flame, Lady Gaga, has been hanging around the East Village bar in the last month, customers have spotted a sign hanging near the telephone that instructs employees to tell callers, “I don’t know Luc.” Carl’s pseudo-celebrity status hasn’t stopped Gaga from stopping by. She visted him Saturday night, sipping red wine at the bar with her bodyguard. “She was playing it really cool. You would not have known they were together,” said a witness